1. Technical Field
The present invention relates to a projector, and more particularly to a technology of projector which displays an image using laser beams as coherent lights.
2. Related Art
When laser beams as coherent lights are applied to a diffusing surface, coherent patterns called speckle noise containing randomly distributed bright points and dark points appear in some cases. The speckle noise is generated by random coherences between diffused lights at respective points on the diffusing surface. The speckle noise recognized during display of an image has undesirable effect on the image to be displayed, since the audience is dazzled by flickering light produced by the speckle noise. For reducing the speckle noise, a technology which produces oscillation of a screen has been proposed in JP-A-2005-107150, for example. According to this technology, a particular speckle pattern becomes relatively inconspicuous by stacking a plurality of speckle patterns created by the oscillation of the screen.
According to a so-called front projection type projector, light is reflected by a screen and observed by the audience. Thus, this projector has an advantage that an image can be observed using various types of screen. However, in the structure which attains reduction of speckle noise based on the construction of the screen, speckle noise becomes conspicuous when a screen other than the dedicated screen is employed. According to the technology in the related art, therefore, it is difficult to reduce speckle noise without imposing any limitation on the types of screen or the like.